The invention relates to a communication system comprising a terminal unit which includes a control circuit and at least two memories for storing software, and comprising a station for supplying software to the terminal unit whose control circuit is provided for exchanging software contained in at least one memory in response to an exchange command.
Such a communication system is known from DE 43 33 272 A1 which discusses a terminal unit coupled to a network and a maintenance device. The maintenance device sends new process software for a control circuit of the terminal unit over the network, which operating software is exchanged in the terminal unit by means of an exchange control unit included in the control circuit. The exchange control unit utilizes exchange software for the exchange operation, which software is stored in an exchange memory. The system software is stored in another memory which is called operating memory. This communication system requires a separate memory (exchange memory) and a separate control unit (exchange control unit) for the exchange operation.